Corrugated plasma trap arrangement for creating a highly efficient downstream microwave plasma system

ABSTRACT

A plasma system is disclosed. The plasma system includes a microwave waveguide assembly having a longitudinal axis parallel with a first axis. The plasma system also includes a plasma tube assembly intersecting the microwave waveguide assembly. The plasma tube assembly has a longitudinal axis parallel with a second axis that is substantially orthogonal with the first axis. The plasma tube assembly also has a plasma-sustaining region defined by an upstream plurality of plasma traps and a downstream plurality of plasma traps.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application contains subject matter that is related to the subjectmatter of the following applications, which are assigned to the sameassignee as this application. The below-listed applications are herebyincorporated herein by reference:

“Methods and Arrangement for Implementing Highly Efficient PlasmaTraps,” by Kamarehi et al., application Ser. No. 11/318,360 filed oneven date herewith.

“Plasma Shield Arrangement for O-rings,” by Wang et al., applicationSer. No. 11/317,517 filed on even date herewith.

“Methods and Arrangement for a Highly Efficient Gas DistributionArrangement,” by Wang et al., application Ser. No. 11/317,961 filed oneven date herewith.

BACKGROUND OF THE INVENTION

Advances in plasma processing have provided for the growth in thesemiconductor industry. As the semiconductor industry has grown,microwave has been utilized as a power source for strip and non-criticaletch applications in substrate processing. Strip applications include,but are not limited to, removing bulk photoresist, post metal etchstrip, passivation for corrosion control, post silicon etch strip, postion implant strip, post poly strip, and post dielectric strip.

One development that has shown continuing promise is the use of new anddifferent geometries in plasma processing machines. Differentgeometries, such as long straight plasma tube and convoluted plasmatube, have been utilized in an attempt to efficiently absorb microwavepower or convert absorbed microwave power into useful plasma species. Tofacilitate discussion, FIG. 1 shows a simple diagram of a prior artconvoluted plasma tube assembly. Plasma 112 may be formed within aplasma tube 102 through the coupling of one or more gases (e.g., O₂, N₂,N₂H₂, HeH₂, water vapor, and fluorinated compounds) with microwavepower, which may have been transmitted by a microwave power generator106 through a waveguide 108. Those skilled in the arts are aware thatconventional plasma tube of one inch or less in diameter may losesignificant percentage of the microwave power that may be generated dueto thermal loading. Since plasma 112 may include both harmful plasmaspecies and useful plasma species, shape and dimension of plasma tubesmay be manipulated to allow for harmful species to recombine into usefulspecies. Consequently, different geometries may translate into higherefficiency apparatuses.

Consider the situation wherein, for example, plasma 112 travels throughplasma tube 102 and encounters a bend 116. As plasma 112 interacts withwalls of plasma tube 102 at bend 116, some of the plasma species mayrecombine. However, with a convoluted plasma tube, the chance forneutral species to recombine may have also increased. As a result, themore convoluted a plasma tube, the less efficient the plasma tube may bein delivering neutral species to a plasma processing chamber.

To reduce the number of useful plasma species from recombining, somemanufacturers may use straight plasma tubes. Without a bend, therecombination rate of plasma species within plasma tube may be reduced.However, manufacturers may have to extend the plasma tube to minimizethe possibility of harmful plasma species from reaching the plasmaprocessing chamber.

Although geometries of plasma tubes may provide a partial solution fordelivering useful plasma species to plasma processing chamber, what areneeded are methods and arrangement for creating a highly efficientdownstream microwave plasma system.

SUMMARY OF INVENTION

The invention relates, in an embodiment, a plasma generation arrangementconfigured to provide plasma downstream to a plasma processing chamber.The arrangement includes a microwave waveguide assembly having alongitudinal axis parallel with a first axis. The arrangement alsoincludes a plasma tube assembly intersecting the microwave waveguideassembly. The plasma tube assembly has a longitudinal axis parallel witha second axis that is substantially orthogonal with the first axis. Theplasma tube assembly also has a plasma-sustaining region defined by anupstream plurality of plasma traps and a downstream plurality of plasmatraps.

In another embodiment, the invention relates to a plasma generationarrangement configured to provide plasma downstream to a plasmaprocessing chamber. The arrangement includes a microwave waveguideassembly having a longitudinal axis parallel with a first axis. Thearrangement also includes a plasma tube assembly intersecting themicrowave waveguide assembly. The plasma tube assembly has alongitudinal axis parallel with a second axis that is substantiallyorthogonal with the first axis. The plasma tube assembly also has aplasma-sustaining region defined by an upstream plasma trap set anddownstream plasma trap set disposed downstream relative to the upstreamplasma traps. The plasma tube assembly further includes a downstreamcooling manifold. The downstream cooling manifold is disposed in one ofa first assembly arrangement and a second assembly arrangement relativeto the downstream plasma trap set. The first assembly arrangement ischaracterized by having substantially no air gap between anupstream-facing surface of the downstream cooling manifold and adownstream-facing surface of the downstream plasma trap set. The secondassembly arrangement is characterized by the downstream cooling manifoldbeing disposed adjacent to the downstream plasma trap set.

In yet another embodiment, the invention relates to a plasma generationarrangement configured to provide plasma downstream to a plasmaprocessing chamber. The arrangement includes a microwave waveguideassembly having a longitudinal axis parallel with a first axis. Thearrangement also includes a plasma tube assembly intersecting themicrowave waveguide assembly. The plasma tube assembly has alongitudinal axis parallel with a second axis that is substantiallyorthogonal with the first axis. The plasma tube assembly also has aplasma-sustaining region defined by an upstream plurality of plasmatraps and a downstream plurality of plasma traps. The downstreamplurality of plasma traps includes at least a downstream outer plasmatrap and a downstream inner plasma trap. The downstream outer plasmatrap is disposed downstream relative to the downstream inner plasmatrap. The arrangement further includes a downstream cooling manifolddisposed in one of a first assembly arrangement and a second assemblyarrangement relative to the downstream outer plasma trap. The firstassembly arrangement is characterized by having substantially no air gapbetween an upstream-facing surface of the downstream cooling manifoldand a downstream-facing surface of the downstream outer plasma trap. Thesecond assembly arrangement is characterized by the downstream coolingmanifold being disposed adjacent to the downstream outer plasma trap.

These and other features of the present invention will be described inmore detail below in the detailed description of the invention and inconjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 shows a simple diagram of a prior art convoluted plasma tubeassembly.

FIG. 2 shows, in an embodiment, a cross-section of a plasma generationarrangement.

FIG. 3 shows, in an embodiment, a simple diagram of a microwavewaveguide assembly.

FIG. 4 shows, in an embodiment, a simple diagram of a gas distributionassembly.

FIG. 5 shows, in an embodiment, a simple diagram of a plasma tubeassembly coupled with a waveguide.

FIG. 6 shows, in an embodiment, a simple diagram of a plurality ofplasma traps.

FIG. 7 shows, in an embodiment, plasma traps with corrugated surfacesand peaks.

FIG. 8 shows, in an embodiment, how corrugated peaks of plasma traps maybe offset.

FIG. 9 shows, in an embodiment, a simple diagram of a cooling assembly.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The present invention will now be described in detail with reference tovarious embodiments thereof as illustrated in the accompanying drawings.In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps and/or structureshave not been described in detail in order to not unnecessarily obscurethe present invention.

In accordance with embodiments of the present invention, there isprovided a plasma generation arrangement within a downstream microwaveplasma system. The plasma generation arrangement may be configured togenerate plasma and channel a portion of the plasma downstream to aplasma processing chamber. In some embodiments, the plasma generationarrangement may have a low profile configuration to enable a moreefficient delivery of useful plasma species to the plasma processingchamber.

FIG. 2 shows, in an embodiment, a cross-sectional view of a plasmageneration arrangement. The plasma generation arrangement may include amicrowave waveguide assembly 210, which may be capable of deliveringmicrowave power to a plasma tube assembly 220. Plasma generationarrangement may also include a gas distribution assembly 230, which mayinject one or more gases into plasma tube assembly 220. Within plasmatube assembly 220, microwave power may couple with one or more gases,such as O₂, N₂, N₂H₂, HeH₂, water vapor, and fluorinated compounds, togenerate plasma 200. Further, plasma generation arrangement may includea plurality of plasma traps 240 to substantially reduce microwaveradiation leakage that may occur. In addition, plasma generationarrangement may include a cooling assembly 260 to reduce thermal loadingthat may occur due to excess power.

FIG. 3 shows, in an embodiment, a simple diagram of microwave waveguideassembly 210, which may include a microwave power generator 212, such asHitachi magnetron, and a waveguide 214. Microwave power generator 212may send microwave power through waveguide 214 to a plasma-sustainingregion 216 of plasma tube assembly 220. Microwave waveguide assembly210, which may have a longitudinal axis parallel with a first axis, mayintersect with plasma tube assembly 220, which may have a longitudinalaxis parallel with a second axis that is substantially orthogonal withthe first axis.

As discussed herein, a waveguide is a rectangular or cylindrical tubedesigned to direct microwave power. Waveguide 214 may extend acrossplasma-sustaining region 216 of plasma tube assembly 220. One end ofwaveguide 214 may include a sliding short 218. By manipulating slidingshort 218, an operator may be able to adjust microwave power deliverywithin waveguide 214.

FIG. 4 shows, in an embodiment, a simple diagram of gas distributionassembly 230. Gas distribution assembly 230 may include a gasdistribution showerhead 232, which may introduce one or more gases intoplasma-sustaining region 216 of plasma tube assembly 220. As notedabove, microwave power may be coupled with gases to create plasma 200.Gas distribution showerhead 232 may further include an ultraviolet (UV)transparent window 234 with an igniter module 236. Igniter module 236may be used to ignite plasma 200.

As noted above, microwave power and one or more gases may couple withinplasma sustaining region 216 to generate plasma 200 that may be neededfor substrate processing. FIG. 5 shows, in an embodiment, a simplediagram of plasma tube assembly 220 coupled with waveguide 214. Plasmatube assembly may be disposed substantially parallel with waveguide 214.Plasma tube 220 may be configured to allow plasma passage down to plasmaprocessing chamber. Plasma tube assembly 220 may be a cylindricalstructure that may be divided into three main sections: an upper section222, a lower section 224, and plasma-sustaining region 216. As discussedherein, a plasma-sustaining region refers to a section of a plasma tubeassembly that may be surrounded by a waveguide. Further, theplasma-sustaining region may be the area in which microwave power andone or more gases may couple to create plasma.

To provide a larger plasma-sustaining region, the geometry of plasmatube utilized has been altered. As noted above, prior art plasma tubesare generally configured having a diameter of about one inch indiameter. In an embodiment, the diameter of plasma tube assembly 220 mayhave a larger diameter than conventional tubes in the prior art.

In the prior art, generation of useful plasma species may reach adiminishing return at approximately 2300 watts due to the thermalloading that may occur in the plasma tube. For typical substrateprocessing using 3000 watts of microwave power at a frequency of 2450MHz in a larger diameter configuration, plasma tube assembly 220 mayprovide for a larger volume in which plasma 200 may be generated. Alarger volume may allow for less thermal loading, which in turn mayresult in a higher rate of absorbed microwave power to couple with oneor more gases to generate plasma species. As discussed herein, plasmaspecies may include both harmful and useful plasma species. Harmfulplasma species may include, but are not limited to, UV photons andenergetic species such as ions. Useful plasma species are usuallyneutral species such as radicals. Whereas harmful plasma species candamage a substrate and/or a process chamber, useful plasma species areneeded to perform strip and/or non-critical etch on a substrate.

In another embodiment, plasma tube assembly 220 may be configured with alow profile in order to decrease wall surface area. With a smaller wallsurface area, useful plasma species may have fewer opportunities tocontact plasma tube assembly wall. Thus, one skilled in the art is awarethat recombination rate may be reduced and the number of useful plasmaspecies delivered to plasma processing chamber for substrate processingmay be increased. The length of plasma tube assembly 220 may bedetermined by several factors including, but not limited to, the size ofwaveguide 214, the profile of plurality of plasma traps 240 (see FIG.2), and the profile of cooling assembly 260 (see FIG. 2).

The size/shape of waveguide 214 may vary depend on microwave wavelengthutilized and the mode for which the waveguide has been selected. Intypical substrate processing, a microwave power generator employed maybe capable of producing 3000 watts of microwave power at 2450 MHz. Tosupport this amount of microwave power and minimize thermal loading,waveguide 214 may be a rectangular waveguide with a transverse electricsub 10 (TE₁₀) mode, in an embodiment.

Another factor that may contribute to the shortened length of plasmatube assembly 220 may be the profile of plurality of plasma traps 240 asnoted above. As discussed herein, plasma traps may be hollow and/orsolid centered electrically conductive disks, which may surround aplasma tube assembly. Plasma traps are generally useful to directmicrowave power and prevent microwave leakage. By preventing microwaveleakage, plasma traps may prevent the extension of plasma beyond awaveguide enclosure resulting in less chance of harmful plasma speciesbeing created near the plasma processing chamber.

FIG. 6 shows, in an embodiment, a simple diagram of plurality of plasmatraps. Plurality of plasma traps 240 may include one or more plasmatraps. Plurality of plasma traps 240 may substantially eliminatemicrowave leakage, especially in process conditions that may include alarge number of operational parameters. In an embodiment, plurality ofplasma traps 240 may include two sets of plurality of plasma traps, anupstream set of plasma traps 244 and a downstream set of plasma traps246.

In an embodiment, upstream set of plasma traps 244 may include anupstream outer plasma trap 244 a and an upstream inner plasma trap 244b. Upstream inner plasma trap 244 b may be disposed above waveguide 214.Upstream outer plasma trap 244 a may be disposed above upstream innerplasma trap 244 b to form a hollow or solid center disk-shapeinterstitial region 244 c. In an embodiment, the interstitial region maybe an air gap or may be filled with a material other than air, such as asolid material.

Similarly, downstream set of plasma traps 246 may include a downstreamouter plasma trap 246 a and a downstream inner plasma trap 246 b.Downstream inner plasma trap 246 b may be disposed below waveguide 214and downstream outer plasma trap 246 a may be disposed below downstreaminner plasma trap 246 b. Between downstream inner plasma trap 246 b anddownstream outer plasma trap 246 a may be a hollow or solid centerdisk-shape interstitial region 246 c, which may be an air gap or may befilled with a material other than air, such as a solid material.

In an embodiment, the surface of each plasma trap (244 a, 244 b, 246 a,and 246 b) may have corrugated surfaces with corrugated peaks as shownin FIG. 7. In an example, downstream inner plasma trap 246 b may have anupstream corrugated surface 254 a and a downstream corrugated surface254 b. On each corrugated surface may be a plurality of corrugated peaks(250 a, 250 b, 250 c, and 250 d). Similarly, downstream outer plasmatrap 246 a may have an upstream corrugated surface 256 a and adownstream corrugated surface 256 b. On each surface may be a pluralityof corrugated peaks (252 a, 252 b, 252 c, and 252 d).

Even though only two plasma traps have been described for each set ofplurality of plasma traps, each set may include any number of plasmatraps. The plurality of plasma traps additionally, within each set, maybe disposed similarly to the plurality of plasma traps described above.Also, each set of plurality of plasma traps may include different numberof plasma traps. In an example, the upstream set of plasma traps mayhave two plasma traps while the downstream set of plasma traps may havethree plasma traps to decrease the risk of microwave radiation leakage.

FIG. 8 shows, in an embodiment, how the corrugated peaks may be offset.In an example, corrugated peaks 250 c and 250 d may be offset relativeto corrugated peaks 252 a and 252 b. By offsetting the corrugated peaks,hollow or solid center disk-shape interstitial regions between each ofthe plasma traps may be minimized, thereby the length of the plasma tubeassembly may be reduced.

As mentioned above, profile of the plurality of plasma traps maycontribute to the profile of the plasma tube assembly. Although lowprofiles traps may be desired, the plurality of plasma traps must belarge enough to prevent microwave leakage and to contain harmful plasmaspecies. Those skilled in the art are aware that traps having a width ofapproximately a quarter of the wavelength of the microwave power may beable to maximize the voltage and minimize the current at the points ofescape, thus, preventing or limiting microwave radiation leakage. In anembodiment, plurality of plasma traps may be corrugated, which mayeffectively reduce the electrical length of microwave power similar tothat of a prior art single trap with dielectric material. Embodiment ofthe invention may further provide for corrugated plurality of plasmatraps to be low profile and still remain effective.

Referring back to FIG. 6, microwave power tends to travel along thelength of the waveguide (paths 242 a and 242 b). Consider the situationwherein, for example, microwave power has been introduced into waveguide214. Microwave power may travel along path 242 a to reach a point 248 awhere waveguide 214 and downstream inner plasma trap 246 b may meet. Atpoint 248 a, impedance may be very high and current may be very low. Inan example, if impedance is as high as infinite then current may bezero. Thus, microwave power may be effectively contained within theplurality of plasma trap and no microwave leakage may occur.

However, if microwave leakage does occur, then the microwave power maytravel along the length of downstream inner plasma trap 246 b to reach acorner 248 b, which may also have very high impedance and very lowcurrent. Hence, any microwave leakage may be effectively containedwithin downstream outer plasma trap 246 a. Similarly, upstream pluralityof plasma traps 244 may capture microwave leakage that may travel alongpath 242 b.

A third factor that may affect the profile of a plasma tube assembly maybe the size of a cooling assembly. FIG. 9 shows, in an embodiment, asimple diagram of cooling assembly 260. Cooling assembly 260 may includea cooling manifold 262 and a hollow cooling jacket 264. Coolant (i.e.,heat-exchange fluid) may flow through cooling manifold 262 and upcooling jacket 264 to reduce thermal loading which in turn may reducethe recombination rate of plasma species.

To shorten the length of plasma tube assembly 220, the height of coolingmanifold 262 may be reduced. However, cooling manifold 262 may stillhave to be large enough to effectively decrease thermal loading. In anembodiment, cooling manifold 262 may be located in close proximity todownstream outer plasma trap 246 a. In an example, an upstream-facingsurface 266 of downstream cooling manifold 262 may be adjacent todownstream-facing surface 256 b of downstream outer plasma trap 246 a.Unlike the prior art, there may be little or no air gap betweendownstream cooling manifold 262 and downstream outer plasma trap 246 a,thereby, reducing the length of plasma tube assembly 220. Similarly, thesame assembly may exist for an upstream cooling manifold in that thedownstream-facing surface of an upstream cooling manifold may beadjacent (i.e. substantially no air gap) to an upstream-facing surfaceof an upstream outer plasma trap.

A coolant (e.g., Fluorinert FC-3283), which may be a microwavetransparent fluid, may flow through cooling manifold 262 and up coolantjacket 264. Cooling jacket 264 may be a substantially cylindrical devicethat may surround plasma tube assembly 220. The coolant flowing throughcooling jacket 264 may interact with plasma tube assembly 220 tofacilitate heat transfer and effectively reduce the thermal loading thatmay occur, especially in plasma-sustaining region 216.

Over time, coolant may cause cooling assembly to deteriorate. In anembodiment, cooling assembly 260 may be made up of ceramic since ceramicmay react less with the coolant than other materials. Further, sinceceramic is opaque to the light spectra emitted by plasma 200, ceramicmay block some of the radiation and may prevent damage to othercomponents of the downstream microwave plasma system.

As can be appreciated from embodiments of the invention, the low profileplasma generation arrangement effectively reduces cost by generatingmore useful plasma species with the amount of microwave power typicallyemployed in normal substrate processing. Thus, a highly efficientdownstream microwave plasma system is created to provide for a more costefficient isotropic substrate processing.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents, which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and apparatuses of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutations,and equivalents as fall within the true spirit and scope of the presentinvention.

1. A plasma system comprising: a microwave waveguide assembly; and aplasma tube assembly intersecting said microwave waveguide assembly,said plasma tube assembly having a plasma-sustaining region defined byan upstream plurality of plasma traps and a downstream plurality ofplasma traps, wherein a first plasma trap among at least one of saidupstream plurality of plasma traps and said downstream plurality ofplasma traps includes a first downstream corrugated outer surface and afirst upstream corrugated outer surface disposed at an opposite side tosaid first downstream corrugated outer surface, said first plasma trapfurther including a first plurality of corrugated peaks protruding, in afirst direction parallel to said plasma tube assembly, outward from saidfirst downstream corrugated outer surface thereby forming said firstdownstream corrugated outer surface, said first plasma trap furtherincluding a second plurality of corrugated peaks protruding, in a seconddirection parallel to said plasma tube assembly and said first pluralityof corrugated peaks, outward from said first upstream corrugated outersurface thereby forming said first upstream corrugated outer surface,and a second plasma trap among at least one of said upstream pluralityof plasma traps and said downstream plurality of plasma traps includes asecond upstream corrugated outer surface and a second downstreamcorrugated outer surface disposed at an opposite side to said secondupstream outer surface, said second plasma trap further including athird plurality of corrugated peaks protruding, in said first directionparallel to said plasma tube assembly, outward from said seconddownstream corrugated outer surface thereby forming said seconddownstream corrugated outer surface, said second plasma trap furtherincluding a fourth plurality of corrugated peaks protruding, in saidsecond direction parallel to said plasma tube assembly and said thirdplurality of corrugated peaks, outward from said second upstreamcorrugated outer surface thereby forming said second upstream corrugatedouter surface, said second upstream corrugated outer surface facing saidfirst downstream corrugated outer surface.
 2. The plasma system of claim1 wherein said first plurality of corrugated peaks includes at least afirst corrugated peak and a second corrugated peak, said firstcorrugated peak surrounding said plasma tube assembly, said secondcorrugated peak surrounding said first corrugated peak.
 3. The plasmasystem of claim 1 wherein said downstream plurality of plasma trapsincludes at least a downstream outer plasma trap and a downstream innerplasma trap, said downstream outer plasma trap being disposed downstreamrelative to said downstream inner plasma trap.
 4. The plasma system ofclaim 3 further including a downstream cooling manifold, said downstreamcooling manifold being disposed in at least one of a first assemblyarrangement and a second assembly arrangement relative to saiddownstream outer plasma trap, said first assembly arrangement beingcharacterized by having substantially no air gap between anupstream-facing surface of said downstream cooling manifold and adownstream-facing surface of said downstream outer plasma trap, saidsecond assembly arrangement being characterized by said downstreamcooling manifold being disposed adjacent to said downstream outer plasmatrap.
 5. The plasma system of claim 4 wherein said downstream coolingmanifold is disposed in said first assembly arrangement relative to saiddownstream outer plasma trap.
 6. The plasma system of claim 4 whereinsaid downstream cooling manifold is disposed in said second assemblyarrangement relative to said downstream outer plasma trap.
 7. The plasmasystem of claim 3 wherein said downstream outer plasma trap is formed ofa first hollow center electrically conductive disk surrounding a passagewithin said plasma tube assembly, wherein a second hollow centerelectrically conductive disk is disposed upstream of said first hollowcenter electrically conductive disk, said second hollow centerelectrically conductive disk also surrounding said passage within saidplasma tube assembly, and a first interstitial region is disposedbetween said first hollow center electrically conductive disc and saidsecond hollow center electrically conductive disc.
 8. The plasma systemof claim 7 wherein said first interstitial region forms an air gap. 9.The plasma system of claim 7 wherein said first interstitial region isformed of a solid material other than air.
 10. The plasma system ofclaim 7 wherein said downstream inner plasma trap is formed of saidsecond hollow center electrically conductive disk, wherein a thirdhollow center electrically conductive disk is disposed upstream relativeto said second hollow center electrically conductive disk, and a secondinterstitial region is disposed between said second hollow centerelectrically conductive disc and said third hollow center electricallyconductive disc.
 11. The plasma system of claim 10 wherein said secondinterstitial region forms an air gap.
 12. The plasma system of claim 10wherein said second interstitial region is formed of a solid materialother than air.
 13. The plasma system of claim 3 wherein said downstreamouter plasma trap is formed of a first solid center electricallyconductive disk surrounding a passage within said plasma tube assembly,wherein a second solid center electrically conductive disk is disposedupstream of said first solid center electrically conductive disk, saidsecond solid center electrically conductive disk also surrounding saidpassage within said plasma tube assembly, and a first interstitialregion is disposed between said first solid center electricallyconductive disc and said second solid center electrically conductivedisc.
 14. The plasma system of claim 13 wherein said first interstitialregion forms an air gap.
 15. The plasma system of claim 13 wherein saidfirst interstitial region is formed of a solid material other than air.16. The plasma system of claim 13 wherein said downstream inner plasmatrap is formed of said second solid center electrically conductive disk,wherein a third solid center electrically conductive disk is disposedupstream relative to said second solid center electrically conductivedisk, and a second interstitial region is disposed between said secondsolid center electrically conductive disc and said third solid centerelectrically conductive disc.
 17. The plasma system of claim 16 whereinsaid second interstitial region forms an air gap.
 18. The plasma systemof claim 16 wherein said second interstitial region is formed of a solidmaterial other than air.
 19. The plasma system of claim 3 furtherincluding an upstream cooling manifold, said upstream cooling manifoldbeing disposed such that there exists substantially no air gap between adownstream-facing surface of said upstream cooling manifold and anupstream-facing surface of an upstream outer plasma trap among saidupstream plurality of plasma traps.
 20. The plasma system of claim 3further including an upstream cooling manifold, said upstream coolingmanifold being disposed adjacent to an upstream outer plasma trap amongsaid upstream plurality of plasma traps.
 21. The plasma system of claim1 wherein said microwave guide assembly includes a sliding shortconfigured for tuning said microwave guide assembly.
 22. A plasma systemcomprising: a microwave waveguide assembly; and a plasma tube assemblyintersecting said microwave waveguide assembly, said plasma tubeassembly having a plasma-sustaining region defined by an upstream plasmatrap set and downstream plasma trap set disposed downstream relative tosaid upstream plasma trap set, wherein a first plasma trap among atleast one of said upstream plasma trap set and said downstream plasmatrap set includes a first plurality of corrugated peaks protruding, in afirst direction parallel to said plasma tube assembly, outward from anouter surface of said first plasma trap thereby forming said outersurface of said first plasma trap, and a second plasma trap among atleast one of said upstream plasma trap set and said downstream plasmatrap set includes a second plurality of corrugated peaks protruding, ina second direction parallel to said plasma tube assembly, outward froman outer surface of said second plasma trap thereby forming said outersurface of said second plasma trap, said second plurality of corrugatedpeaks being aligned with said first plurality of corrugated peaks, saidouter surface of said first plasma trap facing said outer surface ofsaid second plasma trap, said first plasma trap further including athird plurality of corrugated peaks protruding, in said second directionparallel to said plasma tube assembly and said first plurality ofcorrugated peaks, outward from said outer surface of said first plasmatrap thereby forming said outer surface of said first plasma trap, andsaid second plasma trap further including a fourth plurality ofcorrugated peaks protruding, in said first direction parallel to saidplasma tube assembly and said second plurality of corrugated peaks,outward from said outer surface of said second plasma trap therebyforming said outer surface of said second plasma trap.
 23. The plasmasystem of claim 22 further comprising a downstream cooling manifolddisposed such that substantially no air gap exists between anupstream-facing surface of said downstream cooling manifold and adownstream-facing surface of said downstream plasma trap set.
 24. Theplasma system of claim 22 wherein said first plurality of corrugatedpeaks includes at least a first corrugated peak and a second corrugatedpeak, said first corrugated peak surrounding said plasma tube assembly,said second corrugated peak surrounding said first corrugated peak. 25.The plasma system of claim 22 wherein said downstream plasma trap setincludes at least a downstream outer plasma trap and a downstream innerplasma trap, said downstream outer plasma trap being disposed downstreamrelative to said downstream inner plasma trap, wherein said downstreamouter plasma trap is formed of a first hollow center electricallyconductive disk surrounding a passage within said plasma tube assembly,and wherein a second hollow center electrically conductive disk isdisposed upstream of said first hollow center electrically conductivedisk, said second hollow center electrically conductive disk alsosurrounding said passage within said plasma tube assembly, and a firstinterstitial region is disposed between said first hollow centerelectrically conductive disc and said second hollow center electricallyconductive disc.
 26. The plasma system of claim 25 wherein said firstinterstitial region forms an air gap.
 27. The plasma system of claim 25wherein said first interstitial region is formed of a solid materialother than air.
 28. The plasma system of claim 25 wherein saiddownstream inner plasma trap is formed of said second hollow centerelectrically conductive disk, wherein a third hollow center electricallyconductive disk is disposed upstream relative to said second hollowcenter electrically conductive disk, and a second interstitial region isdisposed between said second hollow center electrically conductive discand said third hollow center electrically conductive disc.
 29. Theplasma system of claim 28 wherein said second interstitial region formsan air gap.
 30. The plasma system of claim 28 wherein said secondinterstitial region is formed of a solid material other than air. 31.The plasma system of claim 22 wherein said microwave guide assemblyincludes a sliding short configured for tuning said microwave guideassembly.
 32. The plasma system of claim 22 wherein a downstream outerplasma trap among said downstream plasma trap set is formed of a firstsolid center electrically conductive disk surrounding a passage withinsaid plasma tube assembly, wherein a second solid center electricallyconductive disk is disposed upstream of said first solid centerelectrically conductive disk, said second solid center electricallyconductive disk also surrounding said passage within said plasma tubeassembly, and a first interstitial region is disposed between said firstsolid center electrically conductive disc and said second solid centerelectrically conductive disc.
 33. The plasma system of claim 32 whereinsaid first interstitial region forms an air gap.
 34. The plasma systemof claim 32 wherein said first interstitial region is formed of a solidmaterial other than air.
 35. The plasma system of claim 32 wherein saiddownstream inner plasma trap is formed of said second solid centerelectrically conductive disk, wherein a third solid center electricallyconductive disk is disposed upstream relative to said second solidcenter electrically conductive disk, and a second interstitial region isdisposed between said second solid center electrically conductive discand said third solid center electrically conductive disc.
 36. The plasmasystem of claim 35 wherein said second interstitial region forms an airgap.
 37. The plasma system of claim 35 wherein said second interstitialregion is formed of a solid material other than air.
 38. A plasma systemcomprising: a microwave waveguide assembly; and a plasma tube assemblyintersecting said microwave waveguide assembly, said plasma tubeassembly having a plasma-sustaining region defined by an upstreamplurality of plasma traps and a downstream plurality of plasma traps,wherein a first plasma trap among at least one of said upstreamplurality of plasma traps and said downstream plurality of plasma trapsincludes a first plurality of corrugated peaks protruding, in a firstdirection parallel to said plasma tube assembly, outward from an outersurface of said first plasma trap thereby forming said outer surface ofsaid first plasma trap, a second plasma trap among at least one of saidupstream plurality of plasma traps and downstream plurality of plasmatraps includes a second plurality of corrugated peaks protruding, in asecond direction parallel to said plasma tube assembly, outward from anouter surface of said second plasma trap thereby forming said outersurface of said second plasma trap, said second plurality of corrugatedpeaks being offset relative to said first plurality of corrugated peaks,said outer surface of said first plasma trap facing said outer surfaceof said second plasma trap, said first plasma trap further including athird plurality of corrugated peaks protruding, in said second directionparallel to said plasma tube assembly and said first plurality ofcorrugated peaks, outward from said outer surface of said first plasmatrap thereby forming said outer surface of said first plasma trap, andsaid second plasma trap further including a fourth plurality ofcorrugated peaks protruding, in said first direction parallel to saidplasma tube assembly and said second plurality of corrugated peaks,outward from said outer surface of said second plasma trap therebyforming said outer surface of said second plasma trap.
 39. The plasmasystem of claim 38 further comprising a downstream cooling manifolddisposed such that substantially no air gap exists between anupstream-facing surface of said downstream cooling manifold and adownstream-facing surface of a downstream outer plasma trap among saiddownstream plurality of plasma traps.
 40. The plasma system of claim 38wherein said first plurality of corrugated peaks includes at least afirst corrugated peak and a second corrugated peak, said firstcorrugated peak surrounding said plasma tube assembly, said secondcorrugated peak surrounding said first corrugated peak.
 41. The plasmasystem of claim 38 wherein a downstream outer plasma trap among saiddownstream plurality of plasma traps is formed of a first hollow centerelectrically conductive disk surrounding a passage within said plasmatube assembly, wherein a second hollow center electrically conductivedisk is disposed upstream of said first hollow center electricallyconductive disk, said second hollow center electrically conductive diskalso surrounding said passage within said plasma tube assembly, and afirst interstitial region is disposed between said first hollow centerelectrically conductive disc and said second hollow center electricallyconductive disc.
 42. The plasma system of claim 41 wherein said firstinterstitial region forms a first air gap.
 43. The plasma system ofclaim 41 wherein said first interstitial region forms a first solidstructure.
 44. The plasma system of claim 41 wherein a downstream innerplasma trap among said downstream plurality of plasma traps is formed ofsaid second hollow center electrically conductive disk, wherein a thirdhollow center electrically conductive disk is disposed upstream relativeto said second hollow center electrically conductive disk, and a secondinterstitial region is disposed between said second hollow centerelectrically conductive disc and said third hollow center electricallyconductive disc.
 45. The plasma system of claim 44 wherein said secondinterstitial region forms a second air gap.
 46. The plasma system ofclaim 44 wherein said second interstitial region forms a second solidstructure.
 47. The plasma system of claim 38 wherein a downstream outerplasma trap among said downstream plurality of plasma traps is formed ofa first solid center electrically conductive disk surrounding a passagewithin said plasma tube assembly, wherein a second solid centerelectrically conductive disk is disposed upstream of said first solidcenter electrically conductive disk, said second solid centerelectrically conductive disk also surrounding said passage within saidplasma tube assembly, and a first interstitial region is disposedbetween said first solid center electrically conductive disc and saidsecond solid center electrically conductive disc.
 48. The plasma systemof claim 47 wherein said first interstitial region forms a first airgap.
 49. The plasma system of claim 47 wherein said first interstitialregion forms a first solid structure.
 50. The plasma system of claim 47wherein a downstream inner plasma trap among said downstream pluralityof plasma traps is formed of said second solid center electricallyconductive disk, wherein a third solid center electrically conductivedisk is disposed upstream relative to said second solid centerelectrically conductive disk, and a second interstitial region isdisposed between said second solid center electrically conductive discand said third solid center electrically conductive disc.
 51. The plasmasystem of claim 50 wherein said second interstitial region forms asecond air gap.
 52. The plasma system of claim 50 wherein said secondinterstitial region forms a second solid structure.